For many years it has been known to manufacture sealed battery boxes by interposing a heated platen between the top edge of a battery box and the underneath of a lid to heat co-operating surfaces, removing the platen and pressing the lid onto the box. This apparatus has proved to be extremely satisfactory and there are a large number of such machines in existing manufacturing lines throughout the world. Such batteries usually had a plastic secondary cover or closure which could be clipped onto the lid and removed to allow topping up of the battery. More recent battery developments have enabled manufacturers to design a completely sealed unit in which the secondary closure has to be sealed onto the lid, once the battery has been suitably filled with electrolyte.
It has now been discovered that the majority of lid fixing machines, which exist in the manufacturing lines, are not particularly accurate and small deviations in lid position relative to the battery box occur. This is not only in the lateral and longitudinal positioning of the lid, but also in its orientation.
It is perfectly possible to overcome these problems with better engineering of the lid fixing equipment and the applicants have manufactured a machine which consistently assembles lids with the required accuracy. However, the investment in existing machines is such that this approach only provides a long term solution and currently battery manufacturers are rejecting a significant percentage of batteries because of mis-fitting secondary closures.